Processing of gas oil feedstocks, such as a vacuum gas oil (VGO) feed, and other heavier feedstocks can pose a variety of challenges. One potential difficulty is presented by the boiling point range of the feed. Many of the high value uses of a gas oil feed can require conversion of at least a portion of the molecules in the feed to a lower boiling range. Some typical processes for conversion of feedstocks can include catalytic processes, such as some types of hydroprocessing. Unfortunately, hydroprocessing of such a feedstock can require substantial quantities of catalyst and hydrogen, leading to high costs for processing a feed.
U.S. Pat. No. 7,622,034 describes methods for hydroprocessing of a feed, such as a VGO feed, to produce a diesel product and an FCC feed. The initial feedstock is hydrotreated in a hydrotreatment zone. This produces an effluent that appears to have a sulfur content from about 200-1000 ppm. Some of the effluent from the hydrotreatment zone is then hydrocracked. After fractionation, at least a portion of the effluent that is exposed to hydrocracking is a diesel boiling range feed that appears to have a boiling range of about 140-382° C. and a sulfur content of about 100-2000 wppm. Optionally, a portion of the FCC feed can also be exposed to the hydrocracking. The effluent from the hydrocracking can be exposed to a post-treatment stage to remove any mercaptans formed in the naphtha portion of the hydrocracking product.
U.S. Pat. No. 7,449,102 describes methods for producing hydrocarbon products that include diesel products. The methods include hydrotreating a resid feedstock and separating the hydrotreated effluent into a gaseous and a liquid portion. The gaseous portion is combined with a gas oil feedstock and passed to a hydrocracking stage. In an example provided in the patent, the gas oil feedstock used in the hydrocracking stage has a sulfur content of more than about 2 wt %. The hydrocracked effluent is fractionated, the fractionation possibly resulting in a diesel range product.
U.S. Pat. No. 7,108,779 describes methods for producing hydrocarbon products that include diesel products. The methods include hydrotreating a feedstock and separating the hydrotreated effluent into a gaseous and a liquid portion. Part of the liquid portion is recycled to the hydrotreatment stage, while another part is described as being suitable as a feed for a fluid catalytic cracking process. The gaseous portion is combined with a hydrocarbon feed that boils below about 371° C. and is passed to a hydrocracking stage. The hydrocracked effluent is fractionated, resulting in a diesel range product.
U.S. Pat. No. 6,638,418 describes methods for processing at least two feeds. The first feed is hydrotreated in a first stage. It does not appear that a sulfur content for the hydrotreated effluent from the first hydrotreatment stage is specified. The hydrotreated effluent is then passed into a hydrocracking stage, along with a recycled portion of the hydrocracking effluent. Another portion of the hydrocracked effluent is fractionated to produce at least a low sulfur diesel. A gaseous effluent from the hydrocracking stage is mixed with a second diesel range feed and hydrotreated in a second hydrotreatment stage. This also produces a portion of low sulfur diesel.